Roller cone drill bit that includes components with planar reference surfaces for gauging and inspection

ABSTRACT

The present invention is generally directed to a roller cone drill bit that includes planar reference surfaces for gauging and inspection In one illustrative embodiment, a method of manufacturing a drill bit is disclosed which includes forming a planar reference surface in a ball race of a component of the drill bit, the planar reference surface being substantially perpendicular to a centerline of the component, and using the planar reference surface as a reference point in positioning the component in a manufacturing tool.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally directed to the field of roller cone drill bits, and, more particularly, to a roller cone drill bit that includes components with planar reference surfaces for gauging and inspection.

2. Description of the Related Art

Oil and gas wells are formed by a rotary drilling process. To that end, a drill bit is mounted on the end of a drill string which may be very long, e.g., several thousand feet. At the surface, a rotary drive mechanism turns the drill string and the attached drill bit at the bottom of the hole. In some cases, a downhole motor may provide the desired rotation to the drill bit. During drilling operations, a drilling fluid (so-called drilling mud) is pumped through the drill string and back up-hole by pumps located on the surface. The purpose of the drilling fluid is to, among other things, remove the earthen cuttings resulting from the drilling process.

When the drill bit wears out or breaks during drilling, it must be brought up out of the hole. This requires a process called “tripping,” wherein a heavy hoist pulls the entire drill string out of the hole in stages of, for example, about ninety feet at a time. After each stage of lifting, one “stand” of pipe is unscrewed and laid aside for reassembly (while the weight of the drill string is temporarily supported by another mechanism). Since the total weight of the drill string may be several tons, and the length of the drill string may be tens of thousands of feet, this is not a trivial job. One trip can require many man-hours and, thus, tripping is a significant expense of the drilling budget. To resume drilling, the entire process must be reversed. Thus, the bit's durability is very important to minimize the number of times a bit is replaced during drilling.

Referring now to the drawings in more detail, and particularly to FIGS. 1 and 2, a rolling cutter drill bit 10 includes a body 12 (portions of which are not shown). The body 12 of a typical rolling cutter drill bit 10 comprises three similar leg portions 14 (only two are shown in FIG. 1). A cantilevered bearing spindle 16 (see FIG. 2) formed on each leg 14 extends inwardly and downwardly. A rolling cutter 18 is rotatably mounted upon the bearing spindle 16 as hereinafter explained. Attached to the rolling cutter 18 are cutting inserts 20 which engage the earth to effect a drilling action and cause rotation of the rolling cutter 18.

Typically, each cutting insert 20 will be formed of a hard, wear-resistant material. Internal passageways 22, 24, as well as a reservoir 28, are filled with lubricant (not shown) during bit assembly. The lubricant helps reduce bearing friction and wear during bit operation and is retained within the rolling cutter 18 by a seal 50 in accordance with one illustrative embodiment of the present invention. The seal 50 is positioned in a seal recess 52 (or gland) formed in the rolling cutter 18. Pressure differentials between the lubricant the external environment of the bit are equalized by the movement of a pressure balancing diaphragm 34.

The rolling cutter 18 is mounted upon the cantilevered bearing spindle 16 formed on the leg 14. In some cases, a floating bushing 36 may be mounted on the bearing spindle 16. The floating bushing 36 is designed to carry the radial loads imposed upon the rolling cutter 18 during drilling. Also depicted are a plurality of ball bearings 42. The ball bearings 42 serve to retain the rolling cutter 18 on the bearing spindle 16 by resisting the forces which tend to push the rolling cutter 18 inward during drilling. A thrust face washer 46 may also be positioned between the bearing spindle 16 and the rolling cutter 18. The thrust face washer 46 carries the onward thrust forces imposed upon the rolling cutter 18 during drilling. In operation, the thrust face washer 46 floats in the space between the bearing spindle 16 and the rolling cutter 18. It should be understood that the illustrative bearing configurations depicted in FIG. 2 are provided by way of example only, as the present invention may be employed with any type or configuration of bearings used in mounting the rolling cutter 18 on the bearing spindle 16.

The inserts 20 on the rolling cutters 18 crush and cut the rock as drilling operations are performed with the necessary force being supplied by the “weight-on-bit” (WOB) which presses down on the drill bit 10 and by the torque applied by the rotary drive mechanism. During the drilling process, very large and non-constant stresses and forces are applied to the inserts 20, the rolling cutters 18, and the drill bit 10 itself. Thus, the loads carried by the internal bearings can be very large and irregularly applied. That is, the rolling cutter 18 bearings are subjected to very irregular loads, with the instantaneous loading on the bearings being several times larger than the average bearing loads.

Given the very high loading experienced by the bearings in the dill bit 10 during drilling operations, it is critically important that the bearings be accurately positioned at the desired location. Manufacturing tolerances related to the location of the bearing race 43 for the balls 42 are very small. The bearing race 43 has a radius 41. In some cases, the level of precision involved in locating the ball bearing race 43 in the bearing spindle 16 and/or rolling cutter 18 can adversely increase the axial play of the rolling cutter 18.

Accurate positioning of the ball race radius 41 is very important. For example, it is common to locate or dimension the ball race radius 41 relative to the thrust face 45. This is typically accomplished through use of a paddle-type gauge (not shown). A paddle gauge fits into the radius 41 of the ball race 43. The paddle gauge is used to locate the distance from the thrust face 45 to the center of the ball race 43. Many variables come into play when trying to accurately locate the distance 21 between thrust face 45 relative to the center 19 of the ball race 43. For example, the radius 41 of the ball race 43 must be manufactured with a very high degree of accuracy, the root of the ball race radius 43 must be accurately positioned, and the paddle gauge itself must be very accurate. Variations in any or all of these factors can lead to inaccurate dimensioning or location of the center 19 of the ball race 43 relative to the thrust surface 45. Such inaccurate positioning can lead to problems, such as excessive axial play, which can result in reduced effectiveness of the seal 50 and/or bearings 42, all of which may lead to reduced bearing life and drill bit life.

Both the bearing spindle 16 and the rolling cutter 18 have the race 43 profiled therein to accommodate the ball bearing 42. For purposes of explanation, FIG. 3 is a cross-sectional view of a schematically depicted bearing spindle 16. The centerline of the bearing spindle 16 is indicated by the reference number 17. As indicated therein, the location of the center 19 of the ball race 43 may be referenced by a horizontal dimension 21 relative to the thrust face 45. The very bottom of the ball race 43 may also be referenced by a vertical dimension 23 relative to the centerline 17. Also depicted in FIG. 3 is an illustrative load zone 25 wherein the majority of the bearing loads will be incurred during normal operating conditions. The rolling cutter 18 will have a similar bearing race 43 formed therein that corresponds to the race 43 formed on the bearing spindle 16.

While locating such dimensions on paper is quite easy, it is difficult to precisely locate the position of the bearing race 43 relative to other points, e.g., the thrust face 45 or the centerline 17. In manufacturing roller cutter drill bits 10, each of the bearing spindle 16 and the roller cutter 18 may be subjected to several machining or grinding operations to form the bearing profiles on such components. Such machining and grinding operations may involve the use of several different tools to cut or grind the desired surfaces of such profiles. The accuracy achievable using current gauging and inspection techniques may result in drill bits that exhibit less than desirable performance.

The present invention is directed to devices and methods that may solve, or at least reduce, some or all of the aforementioned problems.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

The present invention is generally directed to various embodiments of a roller cone drill bit that includes planar reference surfaces for gauging and/or inspecting. In one illustrative embodiment, a method of manufacturing a drill bit is disclosed which comprises forming a planar reference surface in a ball race of a component of the drill bit, the planar reference surface being substantially perpendicular to a centerline of the component, and using the planar reference surface as a reference point in positioning the component in a manufacturing tool.

In another illustrative embodiment, the method comprises forming a planar reference surface in a ball race of a bearing spindle of a drill bit, the planar reference surface being substantially perpendicular to a centerline of the bearing spindle, and using the planar reference surface as a reference point in positioning the bearing spindle in a manufacturing tool.

In yet another illustrative embodiment, the method comprises forming a planar reference surface in a ball race of a rolling cutter of a drill bit, the planar reference surface being substantially perpendicular to a centerline of the rolling cutter, and using the planar reference surface as a reference point in positioning the rolling cutter in a manufacturing tool.

In one illustrative embodiment, the drill bit comprises a bearing spindle comprising a bearing race, the spindle having a centerline, a rolling cutter positioned around the spindle, the rolling cutter comprising a bearing race and a centerline, and a planar reference surface formed in the bearing race of at least one of the bearing spindle and the rolling cutter, the planar reference surface being substantially perpendicular to the centerline of the component in which it is formed, i.e., the bearing spindle or the rolling cutter. In some cases, a planar reference surface may be formed in the bearing race of both the spindle and the rolling cutter.

In another illustrative embodiment, the drill bit comprises a bearing spindle comprising a bearing race and a rolling cutter positioned around the spindle. A first planar reference surface is formed in the bearing race of the bearing spindle, wherein the first planar reference surface is substantially perpendicular to a centerline of the bearing spindle. A second planar reference surface is formed in said bearing race of the rolling cutter, wherein the second planar reference surface is substantially perpendicular to a centerline of the rolling cutter.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:

FIG. 1 is a perspective view of a prior art rolling cutter drill bit.

FIG. 2 is a cross-sectional view of a prior art rolling cutter drill bit.

FIG. 3 is a partial cross-sectional view of a schematically depicted prior art spindle depicting the bearing profile of same.

FIG. 4 is a partial cross-sectional view of an illustrative bearing spindle and rolling cutter in accordance with one illustrative embodiment of the present invention.

FIGS. 5A-5B are enlarged partial cross-sectional views of a bearing spindle and rolling cutter of a drill bit in accordance with one embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will, of course, be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

The present invention will now be described with reference to the attached drawings which are included to describe and explain illustrative examples of the present invention. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.

In general, the present invention is directed to the formation of one or more planar reference surfaces on the bearing spindle 16 and/or rolling cutter 18. The planar reference surfaces are substantially perpendicular to a centerline of the bearing spindle 16 and/or rolling cutter 18. In other embodiments, the planar reference surface may be substantially parallel to a thrust face formed on the spindle 16 and/or rolling cutter 18. Such planar reference surfaces may be used in gauging and/or inspecting rolling cutter drill bits 10 in which the accuracy of locating bearings at desired positions may be improved. More specifically, with the improved precision offered through use of the present methodologies disclosed herein, bearing loading may become more uniform and predictable, and bearing life may be increased, as the improved precision may allow for a reduction in axial play.

FIG. 4 is a cross-sectional view of a schematic depiction of an illustrative bearing spindle 16 and rolling cutter 18, each of which have a bearing profile with an illustrative planar reference surface 60H formed therein. Illustrative load zones 25 for the bearings (not shown in FIG. 4) are also depicted. FIGS. 5A and 5B are, respectively, enlarged views of the bearing spindle 16 and rolling cutter 18 depicting the bearing profile of each component.

As shown in FIG. 5A, the bearing spindle 16 comprises a thrust face 45, a ball race 43 having a center 19 and a radius 41, and a planar reference surface 60H. The centerline 17 of the bearing spindle 16 is also shown in FIG. 5A. The planar reference surface 60H is substantially perpendicular to the centerline 17 and substantially parallel to the thrust face 45. The length 47 of the planar reference surface 60H may vary depending upon the particular application, e.g., approximately 0.015-0.020 inches. The planar reference surface 60H is located a horizontal distance 62H from the thrust face 45 on the bearing spindle 16. A similar planar reference surface 60H may be formed on the rolling cutter 18, as indicated in FIG. 5B. The reference surface 60H may be formed at a variety of locations in the race 43. For example, in the depicted embodiments, the reference surface 60H is formed in a region of the race 43 that is located away from the load zone 25. Other locations are also possible. Of course, if desired, more than one reference surface 60H may be formed within a given ball race.

Through use of the planar reference surface 60H depicted in FIGS. 5A-5B, the bearing race 43 may be accurately positioned relative to another surface, such as the thrust face 45. By providing the planar reference surface 60H, the distance between the planar reference surface 60H and the thrust face 45 (or any other substantially parallel surface) may be directly measured by an appropriate instrument, such as a caliper. This is in contrast to the prior art techniques described in the background section of the present application, wherein a paddle instrument was used in an effort to locate the “center” of the race 43. Measurements based upon the prior art techniques suffered from the inherent imprecision in precisely trying to position the paddle at the exact desired location within the race 43. It should be understood that reference to the dimensions as “horizontal” or “vertical” is only provided in a relative sense, it is not meant to imply that the particular surface is horizontal or vertical in an absolute sense. The planar reference surfaces 60H described herein may be formed at any desired point during the manufacturing process. For example, after the thrust face 45 is formed on the bearing spindle 16, the planar reference surface 60H may be formed.

In some cases, the planar reference surfaces described herein to be used as a reference point for adjusting or accommodating variations in a manufacturing tool. For example, in some cases, the cutting tool on a numerically controlled machine tool may need to be changed for a variety of reasons, e.g., wear. In such cases, due to replacement of the cutting tool, the planar reference surfaces described herein may be employed to establish a horizontal offset relative to the surfaces defined by the original worn cutting tool. The numerically controlled machine tool may then be adjusted to compensate for such a variation internally within the tool.

The present invention is generally directed to various embodiments of a roller cone drill bit that includes planar reference surfaces for use in gauging and/or inspection during the manufacture of a rolling cutter drill bit 10. In one embodiment, any tool that is used to machine or grind the race 43 will also be used to machine or grind the reference surface 60H using the same offset. Using this methodology, the variations between the reference surface 60H and the ball race 43 is as small as the inherent accuracy of the manufacturing tool. In effect, this methodology allows the reference surface 60H and the ball race 43 to be treated as a single unit. Given that there are very accurate measurement techniques and instruments for measuring the distance between two parallel flat surfaces (e.g., the reference surface 60H and the thrust face 45), this same accuracy would apply to the thrust face/ball race positioning as well. It should be understood that the thrust face 45, ball race 43, reference surface 60H and centerline 17 may be manufactured in any order. However, the reference surface 60H and ball race 43 are normally “cut as one.”

In one illustrative embodiment, a method of manufacturing a drill bit 10 is disclosed which comprises forming a planar reference surface 60H in a ball race 43 of a component of the drill bit 10 and using the planar reference surface as a reference point in positioning the component in a manufacturing tool. In one particular embodiment, the planar reference surface 60H is substantially perpendicular to a centerline of the component.

In one illustrative embodiment, the drill bit 10 comprises a bearing spindle 16 comprising a bearing race 43, a rolling cutter 18 positioned around the spindle, the rolling cutter 18 comprising a bearing race 43, and a planar reference surface formed in the race of at least one of the bearing spindle 16 and the rolling cutter 18. The reference surface 60H may be substantially perpendicular a centerline of these components. In some cases, a reference surface may be formed in the race 43 formed in each component.

The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below. 

1. A method of manufacturing a rolling cutter drill bit, comprising: forming a planar reference surface in a ball race of a component of said drill bit, said planar reference surface being substantially perpendicular to a centerline of said component; and using said planar reference surface as a reference point in positioning said component in a manufacturing tool.
 2. The method of claim 1, wherein said component comprises at least one of a bearing spindle and a rolling cutter.
 3. The method of claim 1, wherein forming said planar reference surface comprises machining said planar reference surface.
 4. The method of claim 1, wherein forming said planar reference surface comprises grinding said planar reference surface.
 5. The method of claim 1, wherein said planar reference surface and said ball race are formed by a single manufacturing tool.
 6. The method of claim 1, wherein said drill bit component comprises a thrust face and wherein forming said planar reference surface comprises forming said planar reference surface in said component such that it is substantially parallel to said thrust face.
 7. The method of claim 1, further comprising performing a manufacturing operation on said component after positioning said component in said manufacturing tool.
 8. The method of claim 1, wherein said manufacturing tool comprises at least one of a machining tool and a grinding tool.
 9. The method of claim 1, wherein said planar reference surface is formed in a non-loaded area of said ball race.
 10. A method of manufacturing a rolling cutter drill bit, comprising: forming a planar reference surface in a ball race of a bearing spindle of said drill bit, said planar reference surface being substantially perpendicular to a centerline of said bearing spindle; and using said planar reference surface as a reference point in positioning said bearing spindle in a manufacturing tool.
 11. The method of claim 10, wherein forming said planar reference surface comprises machining said planar reference surface.
 12. The method of claim 10, wherein forming said planar reference surface comprises grinding said planar reference surface.
 13. The method of claim 10, wherein said bearing spindle comprises a thrust face and wherein forming said planar reference surface comprises forming said planar reference surface such that it is substantially parallel to said thrust face formed on said bearing spindle.
 14. The method of claim 13, wherein said planar reference surface, said ball race and said thrust face are formed by a single manufacturing tool.
 15. The method of claim 10, wherein said planar reference surface and said ball race are formed in a single manufacturing tool.
 16. The method of claim 10, further comprising performing a manufacturing operation on said bearing spindle after positioning said bearing spindle in said manufacturing tool.
 17. The method of claim 10, wherein said manufacturing tool comprises at least one of a machining tool and a grinding tool.
 18. A method of manufacturing a rolling cutter drill bit, comprising: forming a planar reference surface in a ball race of a rolling cutter of said drill bit, said planar reference surface being substantially perpendicular to a centerline of said rolling cutter; and using said planar reference surface as a reference point in positioning said rolling cutter in a manufacturing tool.
 19. The method of claim 18, further comprising performing a manufacturing operation on said rolling cutter after positioning said rolling cutter in said manufacturing tool.
 20. The method of claim 18, wherein said rolling cutter comprises a thrust face and wherein forming said planar reference surface comprises forming said planar reference surface such that it is substantially parallel to said thrust face formed on said rolling cutter.
 21. The method of claim 18, wherein said planar reference surface, said ball race and said thrust face are formed by a single manufacturing tool.
 22. The method of claim 18, wherein said manufacturing tool comprises at least one of a machining tool and a grinding tool.
 23. The method of claim 18, wherein said planar reference surface and said ball race are formed in a single manufacturing tool.
 24. A rolling cutter drill bit, comprising: a bearing spindle comprising a bearing race, said spindle having a centerline; a rolling cutter positioned around said spindle, said rolling cutter comprising a bearing race and a centerline; and a planar reference surface formed in said bearing race of at least one of said bearing spindle and said rolling cutter, said planar reference surface being substantially perpendicular to said centerline of said at least one of said bearing spindle and said rolling cutter.
 25. The drill bit of claim 24, wherein said planar reference surface is substantially parallel to a thrust face formed on one of said bearing spindle and said rolling cutter.
 26. A rolling cutter drill bit, comprising: a bearing spindle comprising a bearing race, said bearing race having a centerline; a rolling cutter positioned around said spindle, said rolling cutter comprising a centerline; a first planar reference surface formed in said bearing race of said bearing spindle, said first planar reference surface being substantially perpendicular to said centerline of said bearing spindle; and a second planar reference surface formed in said bearing race of said rolling cutter, said second planar reference surface being substantially perpendicular to said centerline of said rolling cutter.
 27. The drill bit of claim 26, wherein said bearing spindle further comprises a first thrust face and wherein said first planar reference surface is substantially parallel to said first thrust face.
 27. The drill bit of claim 26, wherein said rolling cutter further comprises a second thrust face and where in said second planar reference surface is substantially parallel to said second thrust face. 